In an example of a device that comprises a pump, as described in document FR 2 885 887, the device comprises a pump body and a dispenser head that is movably mounted on the pump body to move between a rest position and an activated position in order to deliver a predetermined dose of the substance. When the user desires to use the device, the user presses on the dispenser head so that it takes up its activated position and thus delivers a dose of substance.
It is found that the amount of substance delivered by the device can depend on the force exerted by the user on the movable portion of the device, here made up of the dispenser head. Depending on the force exerted by the user, it is possible to deliver a dose that is incomplete. The fact that the delivered dose is not constant is problematic since it may have non-negligible consequences when the substance is a medicament. Furthermore, in addition to the question of the quantity of substance that is delivered, the force exerted by the user may also affect the quality of a spray, in particular the size of the particles or droplets, and the angle and the density of the spray, which means that it is possible to generate sprays of poor quality. For example, when the dose is delivered with a stop along the stroke, the spray may take the form of a jet, whereas atomization in a mist is expected.